JP3073791B2 - Magenta liquid developer for electrostatography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for electrostatically adhering toner particles to an electrostatic latent image formed on an electrophotographic photosensitive member or an electrostatic recording member to form a visible image and color superimpose. The present invention relates to a magenta liquid developer for photography.

[0002]

2. Description of the Related Art In order to obtain a full-color image by electrophotography or electrostatic recording, an electrostatic latent image is formed on an electrophotographic photosensitive member or electrostatic recording paper by a conventional method, and primary colors are formed in accordance with the destructive color mixing method. It is obtained by electrostatically attaching toner particles in a liquid developer to form a visible image and superimposing colors.

[0003] The liquid developer used in this method comprises a pigment such as rosin, linseed oil, soybean oil, a modified alkyd resin, a styrene butadiene resin, an acrylic resin, etc. It is obtained by pulverizing and dispersing in a carrier liquid having a high insulating property and a low dielectric constant such as an aromatic hydrocarbon.

In color electrophotography, it is desired that the liquid developer has various performances in order to superimpose the toners of the respective primary colors as described above. The reproduction is to be obtained.

[0005] As a pigment generally used for magenta toner, an azo lake pigment represented by Carmine 6B is used because of its good color tone and transparency. However,
All of the toners obtained using the azo lake pigment were inferior in background fog.

In order to improve the color tone of a single-color image without color superposition, a method of adding a specific dye to a specific pigment is generally used. A phenomenon such as image staining occurs.

As another method for improving the color tone of a magenta monochromatic image, a rhodamine pigment and a quinacridone pigment are used as pigments (JP-A-56-75660).
Has been attempted, and a monochrome image having a color tone close to the ideal magenta color has been expressed. However, in the process of expressing a secondary color by color overlay, a magenta color that is more reddish or bluish than the ideal color may be required, depending on the color overlay order and the color tone of other colors. In the above-mentioned pigment mixture system, it is difficult to cope with such a process because the range of adjustment of the color tone (particularly the hue angle) is narrow. Also,
Of these pigment systems, rhodamine-based pigments generally have poor light fastness, which causes a problem that the color tone of an image changes over time.

On the other hand, as a method for eliminating background fog, naphthol AS-based water-insoluble azo pigment, naphthol A
The use of S-benzimidazolone pigments and β-naphthol pigments as toner pigments has also been studied (see, for example,
4-2065, JP-8704662, JP-8704
958) In the liquid developer using these pigments alone, the background fog is improved and other abnormalities are not observed, but the color tone cannot be set arbitrarily and continuously. In some cases, good color reproducibility due to color superposition was not obtained.

[0009]

SUMMARY OF THE INVENTION A first object of the present invention is to set a color tone by arbitrarily setting a color tone according to characteristics of an image output system such as a color superposition order and a color tone of a liquid developer other than magenta. It is an object of the present invention to provide a magenta color liquid developer suitable for a color electrostatic photography of a color development type capable of improving color reproducibility of a secondary color by color superimposition. An object of the present invention is to achieve the above-mentioned problems without causing the above-described problems such as image stains and changes in image color tone over time.

[0010]

Means for Solving the Problems The inventor of the present invention has been studying to solve the above-mentioned problem.
It has been found that the problem can be solved by using a specific pigment in a mixed system of two or more kinds of pigments, and the present invention has been completed.

That is, the present invention relates to a magenta liquid developer for electrophotography comprising toner particles containing a resin dispersed in a carrier liquid and two or more pigments as main components, wherein at least one of the pigments is used. A magenta liquid developer for electrophotography, which is a water-insoluble azo pigment and at least one of the other pigments is a quinacridone pigment.

When two kinds of pigments having hue angles that are too far apart from each other are used as a mixture, the color becomes turbid and loses vividness (decrease in saturation). As a preferred choice, the water-insoluble azo pigment and the quinacridone pigment alone are used as a liquid developer, and the hue angles of the visualized image represented by the LCH color system are 0 to 40 degrees and 330 degrees, respectively. It is better to be 360 degrees.

As the water-insoluble azo pigment, it is preferable to use a naphthol AS-based water-insoluble azo pigment, a benzimidazolone-based water-insoluble azo pigment or a β-naphthol-based water-insoluble azo pigment in terms of reducing background fog. Among them, the following general formula (I) or general formula
It is more preferable to select and use from the pigments represented by (II) or the general formula (III). At this time, a phenomenon (a change in hue angle due to selective electrophoresis) in which only one of the used pigments is selectively consumed during the development process and the color is changed by running without causing background fog is caused. In order not to use the quinacridone pigment, it is more preferable to use a pigment represented by the following general formula (IV).

[0014]

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[0015]

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[0016]

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[0017]

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The naphthol AS-based water-insoluble azo pigment,
Representative examples of the benzimidazolone-based water-insoluble azo pigments, β-naphthol-based water-insoluble azo pigments, and quinacridone-based pigments include the following.

Pigment examples Naphthol AS water-insoluble azo pigment

[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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[0037]

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Benzimidazolone water-insoluble azo pigments

[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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Β-naphthol-based water-insoluble azo pigment

[0045]

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[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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Quinacridone pigment

[0052]

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[0053]

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[0054]

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[0055]

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To prepare a liquid developer using these pigments, a mixture of the above two pigments in an arbitrary ratio is used.
1 to 10 parts by weight, a binder 1 to 50 parts by weight, and a carrier liquid 40 to 100 parts by weight are kneaded and dispersed by an attritor, a ball mill, a sand mill or the like to obtain a concentrated toner, and if necessary, this is mixed with a similar carrier liquid. It may be diluted. Further, in order to control the charge amount in a preferable manner, a commonly used charge control agent such as metallic soap or metal naphthenate may be added as needed at the time of dispersion and / or dilution.

Here, as the binder, alkyd resin,
Rosin-modified phenol formaldehyde resin, polyhydric alcohol ester of hydrogenated rosin, polyacrylic or polymethacrylic ester resin, styrene resin, chlorinated rubber, etc. are used, but in particular mixed resin of the following resin (V) and resin (VI) Use is effective.

Resin (V) Non-aqueous resin obtained by polymerizing at least one kind of styrene-butadiene resin or vinyltoluene-butadiene resin with at least one kind of monomer selected from the following formula (VII): ) Lauryl methacrylate / glycidyl methacrylate / methyl methacrylate (8/1/1) copolymer In order to produce the resin (V), a styrene-butadiene copolymer is dissolved in a non-aqueous solvent, and then a monomer of the general formula (VII) is dissolved. The polymerization reaction may be carried out at a temperature of about 60 to 120 ° C. in the presence of a polymerization initiator such as azobisisobutyronitrile (AIBN) benzoyl peroxide (BPO) which starts polymerization at a relatively low temperature. .

[0059] The monomer represented by the general formula (VII) is a monomer that can be a solvation component even after polymerization, and specific examples thereof include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate, and 2-ethylhexyl acrylate. , Dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl acrylate,
Examples include cetyl methacrylate, cetyl acrylate, vinyl laurate, vinyl stearate, nonyl methacrylate, nonyl acrylate, decyl methacrylate, decyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, and the like.

The polymerization initiator used in the present invention includes:
In addition to AIBN and BPO, phenylazotriphenylmethane, lauroyl peroxide, t-butyl peroxide and the like can be mentioned.

As the carrier liquid used in the developer of the present invention, an aliphatic hydrocarbon or a derivative thereof is preferable. Specific examples thereof include, for example, paraffinic or isoparaffinic hydrocarbons (Isoper H, Isopar G, Isopar L, Isopar K, No. 6 Solvesso manufactured by Esso Corporation).
100), ligroin, n-hexane, n-heptane, iso-octane, n-octane, carbon tetrachloride, trichlorotrifluoroethane, cyclohexane and the like are used alone or in combination of two or more.

Further, other pigments may be used in combination as long as the effects of the present invention are not impaired.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples 1 to 4 A mixture having the composition shown in Table 1 below was placed in a ball mill,
Time-dispersed to make a concentrated toner. A liquid developer was prepared by diluting 30 parts of the concentrated toner with 11 L of Isopar H.

Subsequently, using this liquid developer, printing was performed with an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. In particular, in Examples 3 and 4, images with good magenta color reproducibility showing a color tone (hue angle within ± 5 degrees) originally desired for a liquid developer for electrostatography were obtained. Further, each of the liquid developers of Examples 1 to 4 was developed as a magenta color, and then color superposition development was performed using a yellow liquid developer (hue angle of a yellow single color image: 96.82 degrees) to confirm red color reproducibility. As a result, it was found that the hue angle was continuously changed and the color was well adjusted by the pigment ratio. In particular, the combination of the liquid developer of Example 3 was very close to the ideal color of red (hue angle: 33 degrees), and color reproduction was often performed by color superposition. Table 2 below shows the evaluation results.

Comparative Example 1 The pigment of Example was replaced with CI Pigment Reagent shown in the above-mentioned Pigment Example (7).
A liquid developer for comparison was prepared in the same manner as in Example 1 except that d150 was used alone.

When printing was performed using this liquid developer in the same manner as in the example, no background fog was found as in the example, but the color tone shifted to the red side, and good color reproducibility was not obtained. Examples 1 to 5 using this liquid developer
When color overlay development was carried out in the same manner as in Example 4, the color became red with a strong yellow tint, and satisfactory reproduction was not obtained. Table 2 below
Shows the evaluation results.

Comparative Example 2 The pigment of the example was replaced with the CI Pigment shown in the above-mentioned pigment example (31).
A liquid developer for comparison was prepared in the same manner as in Example 1 except that Red 122 was used alone.

When printing was performed in the same manner as in the example using this liquid developer, no fog was found in the background as in the example, but the color tone shifted to the blue side, and good color reproducibility was not obtained. Examples 1 to 5 using this liquid developer
When color superposition development was carried out in the same manner as in Example No. 4, the color became red with a strong blue tint, and satisfactory reproduction was not obtained. Table 2 below
Shows the evaluation results.

[0070]

[Table 1]

Examples 5 to 8 The pigments 1 and 2 in the above examples were prepared by using the naphthol AS-based water-insoluble azo pigment of the pigment example (5) (CIPigment Red 31).
And quinacridone pigments (CIPigment
Red 209), except that the liquid developers of Examples 5 to 8 were prepared in the same manner as in Examples 1 to 4.

Subsequently, using this liquid developer, printing was performed with an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech Co.). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 3 below shows the evaluation results.

Examples 9 to 12 The pigments 1 and 2 in the above Examples were replaced with the benzimidazolone-based water-insoluble azo pigments (CIPigment Red) of the pigment example (21).
176) and the liquid developers of Examples 9 to 12 were prepared in the same manner as in Examples 1 to 4, except that the quinacridone pigment of Pigment Example (31) was used.

Subsequently, using this liquid developer, printing was performed with an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech Co., Ltd.). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 4 below shows the evaluation results.

Examples 13 to 16 The pigments 1 and 2 in the above examples were prepared by using the benzimidazolone-based water-insoluble azo pigment (CIPigment Red 185) of the pigment example (22) and the pigment example (32)
The liquid developers of Examples 13 to 16 were prepared in the same manner as in Examples 1 to 4, except that the quinacridone pigment was used.

Subsequently, using this liquid developer, printing was performed with an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech Co.). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 5 below shows the evaluation results.

Examples 17 to 20 The pigments 1 and 2 in the above examples were prepared by using the water-insoluble β-naphthol azo pigment (CIPigment Orange 5) of the pigment example (25).
The liquid developers of Examples 17 to 20 were prepared in the same manner as in Examples 1 to 4, except that the quinacridone pigment of Pigment Example (31) was used. Subsequently, using this liquid developer, printing was performed with an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech), and an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 6 below shows the evaluation results.

Examples 21 to 24 Except that Pigment 1 and Pigment 2 in the above Examples were the β-naphthol water-insoluble azo pigment (CIPigment Red 3) of Pigment Example (27) and the quinacridone pigment of Pigment Example (32). Prepared liquid developers of Examples 21 to 24 in the same manner as in Examples 1 to 4.

Subsequently, using this liquid developer, printing was performed by an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech Co.). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 7 below shows the evaluation results.

Examples 25 to 28 Pigment 1 and Pigment 2 in the above Examples were prepared by the following structural formula (VIII)
Example 2 was prepared in the same manner as in Examples 1 to 4, except that the water-insoluble azo pigment of Example 1 and the quinacridone pigment of Example (31) were used.
Five to twenty-eight liquid developers were prepared.

Subsequently, using this liquid developer, printing was performed by an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 8 below shows the evaluation results.

[0082]

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Examples 29 to 32 The same procedures as in Examples 1 to 4 were carried out except that Pigment 1 and Pigment 2 in the above Examples were replaced with a water-insoluble azo pigment represented by the following structural formula (IX) and a quinacridone pigment represented by Pigment Example (32). Example 29 in a similar manner
~ 32 liquid developers were prepared.

Subsequently, using this liquid developer, printing was performed with an electrostatic color printer plotter CE-3436 (manufactured by Versat Tech). As a result, an image in which the color tone was arbitrarily adjusted without background fog was obtained. Table 9 below shows the evaluation results.

[0085]

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[0086]

[Table 2]

[0087]

[Table 3]

[0088]

[Table 4]

[0089]

[Table 5]

[0090]

[Table 6]

[0091]

[Table 7]

[0092]

[Table 8]

[0093]

[Table 9]

* The color tone was measured using a Minolta colorimeter (CR-
121), the Lab value of the image is measured, and H = tan ~
^The comparison was based on the hue angle according to ¹ (b / a). However, the hue angle
For anything beyond 180 degrees, 360 was subtracted from that value.
(The larger the value, the stronger the reddish color.) ** Background fog is the value obtained by subtracting the density of the unprinted background from the density of the background after printing, and the density is a Macbeth reflection densitometer (R
D-914).

In the developer of Example 3 and Comparative Example 1, running was performed while replenishing the developer. As a result, the difference in the color tone of magenta before and after the running was almost the same, and the selective migration of the pigment was not affected. It turned out that it hardly occurred. This can be seen from the fact that the hue angles in Examples 1 to 24 change linearly with the ratio of the pigment used.

Next, a storage test was carried out for three months on the developing solutions of Examples 1 to 32. As a result, no problem was found on the images.

Further, when the images formed using the liquid developers of Examples 1 to 4 were subjected to a light fastness test for 48 hours using a fade meter, deterioration was hardly recognized. Further, the color tone at this time was almost the same as that before the test, and there was no problem of a change in color tone due to deterioration of one pigment.

[0098]

As is clear from the comparison between the examples and the comparative examples, the liquid developer according to the present invention can set the color tone arbitrarily and continuously without causing problems such as background fogging and background staining. It has a remarkable effect such as improvement in color reproducibility when a color image is obtained by color superposition development. Furthermore,
By appropriately adjusting the compounding ratio of the pigment, the hue angle can be adjusted to an appropriate range without side effects. Further, an image formed by the liquid developer of the present invention has excellent light fastness and little change in color tone over time.

In addition, it goes without saying that the present invention can be applied to a color liquid developer for electrostatography for obtaining a monochromatic (arbitrary red) color image by electrostatography.

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/12

Claims (4)

(57) [Claims] 1. A magenta liquid developer for electrophotography comprising toner particles containing a resin dispersed in a carrier liquid and two or more pigments as main components, wherein at least one of the pigments is a water-insoluble azo pigment. Magenta liquid developer for electrophotography, wherein at least one of the other pigments is a quinacridone pigment. 2. A liquid developer comprising a water-insoluble azo pigment and a quinacridone pigment alone, and a hue angle of an image visualized by the LCH color system of 0 to 40 degrees and 330 to 40 degrees, respectively. 2. The magenta liquid developer for electrostatography according to claim 1, wherein the angle is 360 degrees. 3. The electrostatic photograph according to claim 1, wherein the water-insoluble azo pigment is a naphthol AS-based water-insoluble azo pigment, a benzimidazolone-based water-insoluble azo pigment, or a β-naphthol-based water-soluble azo pigment. Magenta liquid developer. 4. A water-insoluble azo pigment represented by the following general formula (I):
Or selected from the pigments represented by the general formula (II) or (III) and selected from the pigments represented by the general formula (IV) as quinacridone pigments. A magenta liquid developer for electrostatography according to the above. Embedded image Embedded image Embedded image Embedded image